The present invention relates to a wiper apparatus for wiping the windows of vehicles. More specifically, the present invention relates to a wiper apparatus having a rise-up mechanism.
There are wipers that have so called rise-up mechanism. In such wipers, wiper blades are stored below their wiping range when not operating so that the visibility of a driver is improved. When the wiper is operating, the wiper blades move into the wiping range and pivot in the range.
Japanese Unexamined Patent Publication NO. 7-165021 describes such a wiper. As shown in FIG. 13, the wiper includes a crank 301, which is rotated by a motor 300. The proximal end of a connecting rod 303 is connected to the distal end of the crank 301 through a shifting mechanism 302. A wiper arm 305 is connected to the distal end of the connecting rod 303 through a link lever 304 at a connecting point. The link lever 304 and the wiper arm 305 integrally pivot about the connecting point. A wiper blade 306 is supported on the wiper arm 305.
When the crank 301 is rotated by the motor 300, rotation of the crank 301 is converted to pivotal movement of the link lever 304 by the connecting rod 303. When the link lever 304 pivots, the wiper blade 306 pivots with the wiper arm 305.
A shaft 307 is provided in the distal end of the crank 301. The shifting mechanism 302 includes an eccentric rotor 308 that is eccentrically rotatable about the shaft 307. The center axis N of the eccentric rotor 308 is offset by a distance H with respect to the shaft 307. The connecting rod 303 is rotatably connected about the axis N of the eccentric rotor 308. The shifting mechanism 302 further includes a first key for fixing the eccentric rotor 308 to the crank 301 and a second key for fixing the eccentric rotor 308 to the connecting rod 303.
When the wiper is not operating, the crank 301 is in an outer position A, the eccentric rotor 308 is positioned as shown by the broken circle A1 in FIG. 13, the second key is released, which permits the connecting rod 303 to rotate with respect to the eccentric rotor 308, and the first key locks the eccentric rotor 308 to the crank 301. The eccentric rotor 308 A5 is fixed to the crank 301 in the position indicated by the broken circle A1. Therefore, the axis N of the eccentric rotor 308 is located on the longitudinal axis of the crank 301 and on an outer side of the shaft 307. In this state, the connecting point between the connecting rod 303 and the link lever 304 is positioned at an upper location A1'. Therefore, the wiper blade 306 is positioned at a lower location A1", which is below a predetermined wiping range R.
When the wiper starts operating, the motor 300 rotates the crank 301 from the position A counterclockwise in FIG. 13. While the crank 301 rotates from the position A to a position C via a position B, the position of the eccentric rotor 308 with respect to the crank 301 is retained. The path of the axis N of the eccentric rotor 308 is shown by the broken line L1. At the same time, the connecting rod 303 rotates about the axis N of the eccentric rotor 308 with respect to the eccentric rotor 308. While the axis N of the eccentric rotor 308 moves on the path L1, the connecting point between the connecting rod 303 and the link lever 304 moves from the position A1' to the position C'. Simultaneously, the wiper blade 306 moves from the storage position A1" to an upper position C of the wiping range R.
When the crank 301 passes the position C, the eccentric rotor 308 is released from the crank 301 by unlocking the first key, and the second key is locked to fix the eccentric rotor 301 to the connecting rod 303. From then on, as long as the crank 301 rotates counterclockwise, the state of the keys does not change. Accordingly, as the crank 301 rotates counterclockwise, the eccentric rotor 308 integrally rotates with the connecting rod 303 about the shaft 307 with respect to the crank 301. A solid-line path L2 shows the movement of the axis N of the eccentric rotor 308.
When the crank 301 reaches the position A again, after one rotation, the eccentric rotor 308 is positioned with respect to the crank 301 at an inner position A2 as shown by a solid-line circle. In this state, compared to the inoperative position A1 indicated by the broken circle, the axis N of the eccentric rotor 308 is offset by a distance 2 H toward the axis of the crank 301. Therefore, the proximal end of the connecting rod 303 is closer to the link lever 304 by the distance 2 H. As a result, the connecting point between the connecting rod 303 and the link lever 304 reverses direction at a limit position A2'. Thus, the wiper blade 306 reverses direction at a corresponding limit position A2" of the wiping range R.
While the crank 301 initially rotates from the position A to the position C as described above, the axis N of the eccentric rotor 308 moves on the broken-line path L1. From then on, as long as the crank 301 rotates counterclockwise, the axis N of the eccentric rotor 308 moves on the solid-line path L2. Accordingly, once the wiper blade 306 moves from the storage position A1" into the wiping range R, the wiper blade 306 swings between the lower position A2" and the upper end position C" of the wiping range R as long as the wiper is operating.
When the wiper is stopped, after reaching the position A, the crank 301 returns to the position A after making one rotation in the reverse direction, or clockwise in FIG. 13. While the crank 301 makes the one clockwise rotation, the initial movement described earlier is reversed. That is, when the crank 301 passes through the position C, the eccentric rotor 308 is released from the connecting rod 303 by the second key, and the first key locks the eccentric rotor 308 to the crank 301. Accordingly, while the crank 301 rotates from the position C to the position A via position B, the axis N of the eccentric rotor 308 moves along the path L1. Therefore, the wiper blade 306 moves from the upper position C" of the wiping range R to the storage position A1".
In the prior art wiper, the operation of the two keys locks the eccentric rotor 308 to the crank 301 or to the connecting rod 303. This change moves the wiper blade 306 between the lower limit position of the wiping range R and the storage position A1".
However, the two keys increase the number of parts and complicate the structure. Complexity increases the cost of manufacturing and lowers reliability.